It is known to provide a plow with a diagonal main beam and to support the plow bottoms on the diagonal frame on vertical pivots so that the plow bottoms may be adjusted. A power source is provided for turning all the plow bottoms in unison. Such a plow is shown in Canadian Patent No. 481,234. It is also known to provide such a frame with a hitch having a tractor vertical connection adjacent the tractor so that the plow may shift relative to the tractor when turning. Conventionally, linkages have extended between the tractor and the rear furrow wheel which cause the rear furrow wheel to steer as the tractor makes its turns. Such linkages are shown in U.S. Pat. Nos. 3,503,453, and 3,817,333. It is also known to provide a rear furrow wheel frame supported on the plow's main frame for swinging movement about a vertical axis so that the wheel frame may swing laterally relative to the main frame. On such plows, the more conventional types of wheel steering mechanism, as above referred to and shown in the above mentioned patents, are incorporated for steering the rear furrow wheel. Also, both of the latter patents provide for adjustable plow bottoms. In each of the latter patents the furrow wheel frame is supported on the vertical pivot on which the rearwardmost plow is mounted and does extend in a fore-and-aft direction. Also, the furrow or rear wheel is positioned in a fore-and-aft disposition and the steering linkages of both patents are composed of four bar linkages that maintain the wheels in such disposition. There are manual turn buckle adjustments for varying the lead of the furrow wheel, but the steering linkage maintains the wheel at the set lead regardless of the width of cut of the plows.
The problems that exist in the aforementioned types of plows is that the linkages for steering the rear wheel are not selfadjusting and consequently do not adjust the lead of the rear furrow wheel in a complimentary relation to various cuts of the plow bottoms. For example, when the plow bottoms are moved to an extremely wide cut it is normally desirable to turn the furrow wheel farther toward plowed ground. This is required for the reason that the wider the cut, the more tendency there is for the plow to move or shift laterally toward the unplowed ground. It would therefore follow that it is desirable in plowing wider cuts to turn the furrow wheel farther toward the plowed ground so as to absorb the greater landside forces. Similarly, as the plow cuts are narrowed, it is desirable to swing the furrow wheel left and in some instances to straighten the rear furrow wheel so that it is in general fore-and-aft disposition. This is one example of the desirability of having a different type of furrow wheel control than the conventional type of linkage extending between the tractor and the rear furrow wheel.
Further, the furrow wheel frame is carried on the main plow frame about a horizontal axis and hydraulic power means are provided to vertically adjust the rear wheel relative to the frame. Since the steering linkage is generally mounted on the main frame, each vertical adjustment of the main frame relative to the wheel frame has the effect of steering the furrow wheel. Such is not desirable and should be compensated for in some manner.